1. Field of the Invention
The present invention relates to an electronic circuit device and more particularly to an integrated circuit device having a plurality of circuit portions, such as emitter-coupled logic (ECL) circuits and transistor-transistor logic (TTL) circuits, formed in the same semiconductor chip, the circuit portions being selectively activated by controlling the power supply voltage.
2. Description of the Prior Art
In general, ECL circuits have the characteristic of a high operating speed, but it is difficult for them to handle large current signals. On the other hand, TTL circuits have the characteristics of a relatively slow operating speed, but it is easy for them to handle large current signals. Therefore, if both types of circuits are used in one integrated circuit (IC) device, it is possible to realize a high performance IC device in which the characteristic of each of the circuits is well utilized.
For example, there is a known programmable read-only memory (ROM) semiconductor IC device which uses both ECL circuits and TTL circuits (Japanese Unexamined Patent Publication No. 51-48944). In this conventional IC device, however, power supply voltages for the ECL circuits and for the TTL circuits are applied to separate power terminals each provided for the TTL or ECL circuits. Therefore, the number of power terminals is large and the switching operation is complicated.